Apparatus for developing high pressure and high temperature

ABSTRACT

An apparatus for developing high temperature and high pressure has a pair of identical dies having opposing cooperating end faces, each face end having therein a spherical cavity and a conically tapering peripheral portion. When the end faces of the two dies are brought closer together, the two spherical cavities conjointly form therebetween a high pressure chamber in which there is received a container made of a plastic material, and the respective peripheral tapering portions form therebetween a gap. The ratio of the radius of curvature of the cavity in each end face to the diameter of this cavity does not exceed 0.75. The volume of the container and its contents is substantially equal to the total volume of the high pressure chamber and the peripheral gap.

States Vereschagin et a1.

[451 July 17, 1973 [76] Inventors: Leonid ll edorovieh Verescliagin,

Kutuzovsky prospekt, 2, ltv. 231, Moscow; Valentin Niltolnevich Bakul, ulitsa Kirova, 34a, kv. 12., Kiev; Ailt Akopovich Semerchan, Kutuzovsky propsekt, 12, kv. 205, Moscow; Alexei iosifovich lPrilthna, ulitsa Vyshgorodskaya, 33, kv. 20, Kiev; Vladimir Vasillievich llopov, ulitsa Chernyshevskogo, 31, ltv. 12, Moscow; Jury Nikolaeviclr Ryabinin, Vorobievskoe shosse, 2, kv. 40, Moscow; Leopold Davydovich Livshits, Gogolevsky bulvar, 23, kv. 25, Moscow; Robert Georgievich Arkhipov, ulitsa Udaltsova, 4, kv. 29], Moscow; Vladislav Nikolaeviclh Slesarev, ulitsa Televidenia, 2/6, korpus 2, kv. 41, Moscow; Vasily Andreevich Galaktionov, 3 Akademichesky proezd, ll, kv. 10, Moscow; Boris llavlovich Demyashkevich, Leningradsky prospekt, 57, lcv. 153, Moscow, all of U.S.S.R.

[22] Filed: Oct. 7, 1971 {21] Appl. No.: 187,269

[52] [1.8. CI. 425/77, 425/D1G. 26

[51] lint. Cl B301) 11/32 [58] Fieldl of Search 425/77, D16. 26

[56] References Cited UNITED STATES PATENTS 3,695,797 10/1972 Bakul et a1 425/DIG. 26

Primary Examiner-J. Howard Flint, Jr. Attorney-Holman & Stern [57] ABSTRACT An apparatus for developing high temperature and high pressure has a pair of identical dies having opposing cooperating end faces, each face end having therein a spherical cavity and a conically tapering peripheral portion. When the end faces ofthe two dies are brought closer together, the two spherical cavities conjointly form therebetween a high pressure chamber in which there is received a container made of a plastic material, and the respective peripheral tapering portions form therebetween a gap. The ratio of the radius of curvature of the cavity in each end face to the diameter of this cavity does not exceed 0.75. The volume of the container and its contents is substantially equal to the total volume of the high pressure chamber and the peripheral gap.

2 Claims, 3 Drawing Figures APPARATUS FOR DEVELOPING HIGH PRESSURE AND HIGH TEMPERATURE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to apparatus for developing high pressure and high temperature, and, more superhard it relates to apparatus for performing the synthesis of super materials, such as artificial diamonds and cubical boron nitride.

2. Description of the Prior Art Among the most desired properties of a highpressure apparatus used either for research or, more particularly, for industrial production of superhard materials, are the simplicity of structure and ease of operation.

The most simple types of apparatus for the above purpose have been described by Ballhausen in the periodical magazine VDI Z Bd 105, Nov. 15, 1963 (III), pp. 617-623.

An apparatus described in the above said periodical comprises a pair of dies firmly supported at the lateral sides thereof, the dies having each a spherical cavity of a shape closely approaching a hemisphere, the two cooperating cavities receiving thereinside a container made of a thermally and electrically insulating material, for instance, of pyrophillite. A heating element and a sample to be compressed are placed into the container. The ratio of the external diameter of each die to the diameter of the cavity therein is in excess of 2.0.

When the abovedescribed die assembly is compressed in a press, the material of the container is subjected to plastic deformation and at first partly flows into gap left between the dies, the gap continuously narrowing as the dies are driven toward each other, thus partly compressing the sample placed in the container. When the gap between the end faces of the dies is narrowed to a certain width, the flow of the material of the container into the gap is practically discontinued, and as the dies are brought still further together, the cavity is sealed with the volume thereof decreasing, and the decrease of the volume of the now sealed cavity formed therebetween builds up the pressure inside the cavity.

In the abovedescribed apparatus there have been achieved pressures as high as 35 kilobars, but, however, pressures this high are insufficient in certain cases, e.g. for synthesis of diamonds. The fact that the cavities of the dies are shaped as hemispheres makes it virtually impossible to achieve higher pressures.

In the abovedescribed known apparatus the gap between the dies is not completely filled by the material of the container, and as a result the dies do not become firmly cemented together, and, consequently, the strength of the die assembly at pressures in excess of 40 kilobars might be insufficient.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus for developing pressures in excess of 40 kilobars and high temperatures which are sufficient, for instance, for synthesis of artificial diamonds.

It is another object of the present invention to provide an apparatus which is capable of reliable operation during a plurality of successive loading and heating cycles, with the dies being firmly and sealingly held together in the gap area.

In order to accomplish the abovespecified and other objects, in an apparatus for developing high pressure and high temperature, comprising a pair of substantially identical cooperating dies, each said die having in an end face thereof a spherical cavity and a conically tapering peripheral surface portion surrounding said cavity, said dies being so positioned that when said end faces thereof are pressed in assembly toward each other, said respective cavities in the cooperating dies conjointly form a high pressure chamber adapted to receive a container made from a thermally and electrically insulating material displaying plasticity under compression from all sides; said insulting material is adapted to flow, as said dies are driven together, into the gap formed between the respective conically tapering peripheral surface portions of said end faces of said dies; in accordance with the present invention, the ratio of the radius of the curvature of the curved surface of said cavity in each said die to the diameter of said cavity does not exceed 0.75, and the volume of said container is so selected, that the total volume of said material of said container and of the contents thereof is substantially equal to the total volume of said high pressure chamber and said gap left between said respective peripheral portions of said end faces of said dies.

According to a preferred embodiment of the present invention, the ratio of an external diameter of the die to the diameter of the cavity in the face end thereof is maintained within the ranges 1.7 to 1.8 limits.

BRIEF DESCRIPTION OF THE DRAWING The present invention will be better understood from the following description of an embodiment thereof, with reference being had to the accompanying set of drawings, wherein:

FIG. 1 is a diametrically sectional view of an appara tus for developing high pressure and high temperature, constructed in accordance with the invention;

FIG. 2 is an enlarged part view of the apparatus shown in FIG. 1, with the two dies having been brought closer together;

FIG. 3 is a diagram showing a curve representing the pressure in the high pressure chamber of the apparatus against the compressing effort applied to the two dies.

Referring now in particular to the appended drawings, the apparatus for developing high pressures and temperatures includes a pair of substantially identical cooperating dies 1 (FIG. 1 each die 1 having a central cavity in and end face thereof, the cavity being shaped similar to a segment of a sphere, each die including a tapering peripheral surface surrounding the cavity. Each die 1 is firmly embraced by a ring 2 made of highstrength steel, the ring 2 engaging the side wall of the respective die 1. Disposed between the end faces of the two dies 1 is a container 3 made either from lithographic stone, or from talc, or else from pyrophillite.

Shown in the FIG. 2 is an enlarged part view of the highpressure chamber defined by the cavities of the two cooperating dies 1, and the gap 5 formed between the respective tapering surfaces of the face ends of the dies 1, when the two dies are forcibly brought together. The numeral 4 in FIGS. I and 2 indicates a sample subjected to the high pressure developed by the dies, the sample being assembled with a heater element, e.g. graphite heater, of any commonly known type.

Development of extremely high pressures, in excess of 40 kilobars, in the herein disclosed apparatus is provided for by establishing an appropriate ratio of the radius of the spherical surface of the cavity in the die to the diameter of the cavity. It has been found that this ratio should not exceed 0.75.

The die itself has been found to possess sufficient strength when the external diameter (D) thereof is 1.7 to 1.8 times greater than the diameter (d) of the cavity, and when there are established such conditions that during the process of developing high pressures between the two cooperating dies, at least when the pressures exceed 20 25 kilobars, each die is in a state of complete compression from all sides.

Experimental studies which have been carried out with apparatus of the herein disclosed kind have shown that the operational characteristics thereof expressed as a curve representing the compressing force 6 against the intensity of pressure 7 developed in the chamber (FIG. 3) are not proportional, i.e., the curve is not rectilinear, the angle of the inclination thereof decreasing in the area of high pressures. When the angle of the inclination of this curve to the ordinate axis in the area of the high pressures is too small, there is a possibility that the dies might either be damaged or destroyed by the great compressive forces, or else might become plastically deformed before the desired pressure is developed. Thus, when a pressure as high as 50 to 90 kilobars is to be developed with the dies made of tungstencobalt hard alloy, known under the trade name of carballoy, the ratio of the curvature radius (R) of the spherical cavity in the die to the diameter (d) of the cavity should not exceed 0.75, and the volume of the container 3 should be so selected that at the completely compressed state of the two dies the volume of the material of the container 3 itself plus the volume of the material received inside the container should be as close as possible to the total volume of the high pressure chamber and the sealing gap between the tapering surfaces of the two dies 1.

When the last-mentioned requirement is satisfied, the external diameter of the extruded shoulder portion 8 of the container 3, sealing away the high pressure chamber and cementing together the opposing end faces of the two dies 1 in the compressed state of the apparatus becomes substantially equal to the external diameter D of the dies, which means that the volume of the container 3 has been properly selected.

The herein disclosed apparatus operates, as follows.

The reaction composition together with the electrical heater, indicated in the appended drawings as the sample 4, is positioned in the container 3. The container 3 in this assembled state is placed in the high pressure chamber formed between the opposing end faces of the spaced dies 1. Then the two dies 1 are driven toward each other under the action of an associated press (not shown), whereby the peripheral area of the container 3 becomes gradually deformed and fills the gap 5. The plastic flow of the material of the container 3 being lim ited when, the compression stroke of the associated press progresses the desired pressure is developed within the high pressure chamber.

Electric power, i.e., voltage for heating the sample 4 can be supplied to the heater of the sample through the dies 1, in which case at least one of the two dies should be electrically insulated from the rest of the press structure.

What is claimed is:

1. An apparatus for developing high pressure and high temperature, comprising: a pair of substantially identical die means for developing high pressure when in assembly, said die means being made from a mechanically strong material and having respective end faces opposing each other, each said end face having therein a cavity formed in the shape of a segment of a sphere, each said end face also having a conically tapering peripheral surface portion in continuation of and surrounding said cavity, said pair of die means being so positioned that when they are driven toward each other in assembly said cavities combinedly form therebetween a high pressure chamber and said respective peripheral tapering surface portions thereof form therebetween an annular gap; a container made from a thermally and electrically insulated material displaying plasticity under compression from all sides, disposed in said high pressure chamber, the dimensionsof said container being so selected that the total volume of said material of said container and of the contents thereof is substantially equal to the total volume of said high pressure chamber and said annular gap formed between said pair of die means when they are driven toward each other, the apparatus characterized in that the ratio of the radius of the curvature of the surface of said cavity of each said die means to the diameter of said cavity being not in excess of 0.75.

2. An apparatus, as set forth in claim 1, wherein the ratio of the external diameter of each said die means to said diameter of said cavity at said end face thereof is within the range 1.7 to 1.8. 

1. An apparatus for developing high pressure and high temperature, comprising: a pair of substantially identical die means for developing high pressure when in assembly, said die means being made from a mechanically strong material and having respective end faces opposing each other, each said end face having therein a cavity formed in the shape of a segment of a sphere, each said end face also having a conically tapering peripheral surface portion in continuation of and surrounding said cavity, said pair of die means being so positioned that when they are driven toward each other in assembly said cavities combinedly form therebetween a high pressure chamber and said respective peripheral tapering surface portions thereof form therebetween an annular gap; a container made from a thermally and electrically insulated material displaying plasticity under compression from all sides, disposed in said high pressure chamber, the dimensions of said container being so selected that the total volume of said material of said container and of the contents thereof is substantially equal to the total volume of said high pressure chamber and said annular gap formed between said pair of die means when they are driven toward each other, the apparatus characterized in that the ratio of the radius of the curvature of the surface of said cavity of each said die means to the diameter of said cavity being not in excess of 0.75.
 2. An apparatus, as set forth in claim 1, wherein the ratio of the external diameter of each said die means to said diameter of said cavity at said end face thereof is within the range 1.7 to 1.8. 